Innovation Description and Benefit:

The empirical slab design is an AASHTO-LRFD specification that reduces the amount of reinforcing steel in bridge decks. Laboratory testing revealed that deck loads are transferred mostly through arching action in the deck and not shears and moments as traditionally designed for. Once geometric specifications for the deck are met, a specified reinforcement ratio is used to determine the amount of longitudinal and transverse steel. No other design calculations are required for the interior of the deck. Additional transverse bars are placed in the overhang to support the barrier sitting on the cantilevered edge of the deck. Because of the size of MoDOT’s standard bridge barrier compared to this slab design, a Texas DOT barrier that is smaller and lighter than MoDOT’s type D barrier but has the same AASHTO test level can be used. The TxDOT barrier is 36 inches tall, TL-4 rated, and 1.5 inches narrower than MoDOT’s Type D or Type H barrier. The empirical slab design and TxDOT SSTR barrier combination is being used on 19 bridge replacements in the Northwest Bridge Bundle Design-Build Project. All completed, empirical slab design bridges will be 180 feet or less and 18 of them will be three spans or less. The AADT of each roadway is less than 600.